Electric hand tools are usually equipped with an electric motor, which can drive a cutting or drilling tool, in general a chip-removing tool. In electric hand tools, which contain milling tools, it is desirable to increase its potential uses by means of attachments in order to open up a broader application spectrum to the electric tool user.
EP 0 830 923 A1 has disclosed an electrically driven hand tool. This includes a motor disposed in a housing, and a vertically adjustable milling head that is driven by the motor via a transmission. The disclosure of the device in EP 0 830 923 A1 proposes placing the electric motor of the hand tool in a horizontal position so that its drive shaft is disposed essentially perpendicular to the rotational axis of the milling head and a first adjusting device permits a manual, tool-free adjustment of the milling head in the vertical direction without changing the position of the motor and of the transmission. In addition, the known embodiment is provided with a second adjusting device, which permits a manual, tool-free lateral pivoting of the milling head.
This configuration of an electric hand tool known from the prior art is provided with two independently actuatable adjusting devices, one of which permits a vertical adjustment of the milling head, while the other adjusting device on the electric hand tool permits a lateral pivoting of the milling head. Since the second adjusting device extends essentially parallel to the drive shaft of the milling head, then there is no room to connect attachments such as parallel fences or circular stops next to the opening that encompasses the milling tool. This is essentially due to the orientation of the second adjusting device in the hand tool known from EP 0 830 923 A1 so that connecting and reliably securing attachments to this hand tool, which expand its potential uses, is hardly possible or can only be achieved for an increased cost.
Numerous advantages for operator using the electric hand tool, which is improved according to the invention, can be inferred from the embodiment proposed according to the invention. The function of an electric hand tool with an electric drive unit can be expanded in a multi-faceted way simply through the detent locking the mounting section of a mounting rail.
On the mounting rail itself, which can be comprised of U-shaped profiles that are slid into each other and are made of a metallic material or also of plastic, a compass point is provided on a carriage-shaped component and locking mechanisms are provided for the installation of a parallel fence. The parallel fence, which can be comprised of metal or shock-resistant plastic, can be fixed in its respective operating position on the mounting rail by means of a half turn or a three-quarter turn of a locking screw. The guide surface of the parallel fence is interrupted approximately in the middle by a recess, which in semicircular fashion, encompasses the chip-removing tool held in the chuck of the electric hand tool, regardless of whether it is a milling head, a drill bit, or a cutting tool.
With the compass point, which can be slid in relation to the mounting rail in a carriage-shaped component on the mounting rail, circular cutouts can be made in a wide variety of materials. Extremely small diameters of down to approx. 20 mm can be produced with precision due to the proximity of the compass point to the cutting tool mounted in the symmetry axis of the electric tool. The guidance of the electric hand tool around the inserted compass point when cutting out circles is facilitated by means of a turning handle mounted onto the end remote from the compass point. An adjustment of the radius"" of the circle to be cut out can be simply executed by loosening the locking screw on the mounting rail and then sliding the two U-shaped profiles of the mounting rail in relation to each other. When cutting out circles, depending on the reduction of the movable points of intersection, a stable introduction of force is permitted, which permits precise operation to be executed. Only the mounting section of the mounting rail is detent connected to the mounting base of the electric hand tool and is therefore locked in the operating position. After a relative sliding of the U-shaped profiles of the mounting rail and adjustment of the cutting radius"", all of the possible relative movements have been exhausted, thus assuring a virtually play-free disposition of the components in relation to one another.
One of the U-shaped profiles of the mounting rail, preferably comprised of a metallic material, is cast into the mounting section comprised of plastic. A compass point, preferably provided on a carriage-shaped component, can be disposed on one of the U-shaped profiles of the mounting rail; the parallel fence can be inserted into the relevant U-shaped profile to which the carriage-shaped component with the compass point mounted on it can be attached and, after a half turn or three-quarters turn of the locking screw, can be fixed to a clamping rail embodied in the U-shaped profile.
The mounting section of the mounting rail is fixed in position by means of a wire clip with rotation prevention means, which is inserted into the mounting section. For this purpose, the ends of the multiply deformed wire clip are inserted into mounting bores of the mounting section. When enclosing the mounting base of an electric hand tool, the multiply deformed sections, i.e. the detent projections of the shaped clip, engage in a recess of the mounting base of the electric hand tool at several locations. By exerting tension on a clamping yoke by means of a cam lever, the mounting section of the mounting rail can be simply and rapidly locked in a tool-free manner to the mounting base of the electric hand tool.
The embodiment proposed according to the invention of a mounting section, which can be coupled in a tool-free manner to the mounting base of an electric hand tool and is for function-expanding attachments such as parallel fences and compass point cuts, is distinguished by means of its extremely simple operation. An easily accessible clamping yoke device makes it possible in particular to fix the mounting section and the mounting base to each other in a non-rotatable fashion in a first operating position. In another, second operating position, the mounting section is secured in the axial direction by a shaped clip that can be inserted, but is held so that it can rotate freely in relation to the mounting base, which is very useful for producing circular cutouts in a work piece.
A mounting rail protruding radially from the mounting section can, in order to increase the operational safety, be secured at opposite pointsxe2x80x94e.g. in the form of recessesxe2x80x94in an annular wall of the mounting section, which assures a particularly safe operation. Openings that are oval or extend in the longitudinal direction of the mounting rail allow the operator to see the work piece and the cut being made in it.
The end of the mounting section oriented toward the mounting base of the electric hand tool can be provided with support surfaces, which absorb the forces of pressure exerted by the tool operator, which permits the achievement of a uniform introduction of force into the mounting section. A parallel fence can be mounted to a mounting section with mounting rails with particular ease due to the fact that the parallel fence is secured to a carriage, which can travel on the mounting rail, by means of detent locking mechanisms whose position in detent openings is assured by means of a frictional/positive engagement between the detent locking elements, which can be embodied as detent knobs that a detent surface can slide past.